Re: [PATCH v2 1/6] linux-user/aarch64: Extend PR_SET_TAGGED_ADDR_CTRL for FEAT_MTE3

[Gustavo Romero <gustavo.romero@linaro.org>]

On 2/6/24 12:05 AM, Richard Henderson wrote:
> When MTE3 is supported, the kernel maps
>    PR_MTE_TCF_ASYNC | PR_MTE_TCF_SYNC
> to
>    MTE_CTRL_TCF_ASYMM
> and from there to
>    SCTLR_EL1.TCF0 = 3
> 
> There is no error reported for setting ASYNC | SYNC when MTE3 is not
> supported; the kernel simply selects the ASYNC behavior of TCF0=2.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   linux-user/aarch64/target_prctl.h | 25 +++++++++++++------------
>   1 file changed, 13 insertions(+), 12 deletions(-)
> 
> diff --git a/linux-user/aarch64/target_prctl.h b/linux-user/aarch64/target_prctl.h
> index 5067e7d731..49bd16aa95 100644
> --- a/linux-user/aarch64/target_prctl.h
> +++ b/linux-user/aarch64/target_prctl.h
> @@ -173,21 +173,22 @@ static abi_long do_prctl_set_tagged_addr_ctrl(CPUArchState *env, abi_long arg2)
>       env->tagged_addr_enable = arg2 & PR_TAGGED_ADDR_ENABLE;
>   
>       if (cpu_isar_feature(aa64_mte, cpu)) {
> -        switch (arg2 & PR_MTE_TCF_MASK) {
> -        case PR_MTE_TCF_NONE:
> -        case PR_MTE_TCF_SYNC:
> -        case PR_MTE_TCF_ASYNC:
> -            break;
> -        default:
> -            return -EINVAL;
> -        }
> -
>           /*
>            * Write PR_MTE_TCF to SCTLR_EL1[TCF0].
> -         * Note that the syscall values are consistent with hw.
> +         * Note that SYNC | ASYNC -> ASYMM with FEAT_MTE3,
> +         * otherwise mte_update_sctlr_user chooses ASYNC.
>            */
> -        env->cp15.sctlr_el[1] =
> -            deposit64(env->cp15.sctlr_el[1], 38, 2, arg2 >> PR_MTE_TCF_SHIFT);
> +        unsigned tcf = 0;
> +        if (arg2 & PR_MTE_TCF_ASYNC) {
> +            if ((arg2 & PR_MTE_TCF_SYNC) && cpu_isar_feature(aa64_mte3, cpu)) {
> +                tcf = 3;
> +            } else {
> +                tcf = 2;
> +            }
> +        } else if (arg2 & PR_MTE_TCF_SYNC) {
> +            tcf = 1;
> +        }
> +        env->cp15.sctlr_el[1] = deposit64(env->cp15.sctlr_el[1], 38, 2, tcf);
>   
>           /*
>            * Write PR_MTE_TAG to GCR_EL1[Exclude].
> 

Reviewed-by: Gustavo Romero <gustavo.romero@linaro.org>